1. Field of the Invention
The present invention relates to a rotating electrical machine, and particularly relates to a liquid-cooled rotating electrical machine.
2. Description of Related Art
At a front wheel, rear wheel, or four-wheel drive vehicle that is mainly powered by a rotating electrical machine only or an engine and a rotating electrical machine, the rotating electrical machine is fitted between the engine and a transmission or is fitted within the transmission and the rotating electrical machine is mechanically connected to the engine and the transmission. Rises in temperature are problematic because the rotating electrical machine is a compact, high-output rotating electrical machine. It is therefore necessary to rapidly dissipate heat generated at the stator core and coils of the rotating electrical machine used as the main power of the vehicle.
The rotating electrical machine used as the main power of the vehicle is cooled by a dedicated coolant for dissipating heat. Alternatively, the coolant can also function as lubricating oil for a transmission or decelerator when the rotating electrical machine is built into a transmission or decelerator. This both increases the cooling performance of the rotating electrical machine and brings about a compact, high output rotating electrical machine.
The rotating electrical machine used as the main power for the vehicle is required to both be compact and have a high output. This means that the use of a centralized or concentrated winding type stator structure is common. When a centralized winding type stator structure is adopted, a stator side armature includes an annular stator core, a bobbin that is an insulator that covers a teeth section of the stator core, and a coil formed by winding a conductor around the bobbin. The bobbin is an important part that both provides insulation between the coil and the core and acts as a shape supporting member for the coil. Resin molded articles are typically used as the bobbin. The thermal conductivity of such resin molded articles is extremely low compared to metal components such as the stator coil and core.
Technology is disclosed as a method of cooling a rotating electrical machine where circular plates that force the coolant to flow at both coil ends of the rotating electrical machine are provided so that the coolant is moved to trace each coil. This increases the heat dissipating effect. Such technology is disclosed in Japanese Laid-open Patent Publication No. 2006-197772 (patent document 1).
Technology is also disclosed where a cooling groove is provided at a portion of the bobbin the coil is wrapped around. Cooling then takes place from the inside of the coil. Such technology is disclosed in Japanese Laid-open Patent Publication No. 2005-57884 (patent document 2).
Technology for insulating between the coil and the stator core and supporting the coil shape is also disclosed where an engaging member (projecting section positioned between conducting wires) is provided on the cylindrical section of the bobbin that the coil wires (conducting wires) are wound around so as to restrict the position of winding of coil wires. The coil wires are then wound around this engaging member. This means that a gap created between the coil wires and collapsing of the coil wires upon completion of winding are prevented. The coil wire for the first layer can therefore be wound in an orderly manner. Such technology is disclosed in Japanese Laid-open Patent Publication No. 2006-67778 (patent document 3).
Unfortunately, in patent document 1, the path taken by the coolant is such that the coolant only makes direct contact with surfaces of the coil ends. This means that a portion on the inside of the coil end that makes contact with the stator core that can be considered to be the portion of a centralized winding type stator that heats up the most is not cooled.
In patent document 2, it is necessary for the coil and the stator core to face each other via the cooling groove in order to form the cooling groove in the bobbin. This creates problems with regards to insulation.
With the bobbin disclosed in patent document 3, bobbin brims are provided to the outer diameter side and the inner diameter side of the coil in order to prevent the coil winding from collapsing. However, this degrades cooling efficiency because the surface area of the coil the coolant flows when a motor is cooled directly by the coolant collides with is reduced by the brims.
It is therefore an object of the present invention to provide a rotating electrical machine with improved cooling performance that is capable of maintaining insulation.